Rotatable cutting tools have been used to impinge earth strata, such as, for example, asphaltic roadway material or ore bearing or coal bearing earth formations, or the like. Generally speaking, these kinds of rotatable cutting tools have an elongate cutting tool body typically made from steel and a hard tip (or cutting insert) affixed to the cutting tool body at the axial forward end thereof. The hard tip is typically made from a hard material such as, for example, cemented (cobalt) tungsten carbide. The rotatable cutting tool is rotatably retained or held in the bore of a tool holder or, in the alternative, in the bore of a sleeve that is in turn held in the bore of a holder.
The holder is affixed to a driven member such as, for example, a driven drum of a road planing machine. In some designs, the driven member (e.g., drum) carries hundreds of holders, wherein each holder carries a rotatable cutting tool. Hence, the driven member may carry hundreds of rotatable cutting tools. The driven member is driven (e.g., rotated) in such a fashion so that the hard tip of each one of the rotatable cutting tools impinges or impacts the earth strata (e.g., asphaltic roadway material), thereby fracturing and breaking up the material into debris.
As can be appreciated, during operation the rotatable cutting tool and the cutting insert are typically subjected to a variety of extreme cutting forces and stresses in an abrasive and erosive environment. The overall total length of the cutting insert, and in particular, the length that the cutting insert extends from the axial forward end of the cutting tool, determines the amount of forces and stresses that are transmitted to the cutting tool during operation. In other words, the more the cutting insert extends from the cutting tool, the larger the forces and stresses that will be generated, which may result in tool failure.